Harmonically and fundamentally mode-locked InGaAs-AlGaAs disk laser generating pulse repetition rates in the 100 GHz or pulse durations in the 100-fs range

Abstract

Femtosecond mode-locked semiconductor disk lasers (SDLs) have the potential to replace rather complex, expensive laser systems and to establish ultrashort-pulse applications outside of scientific laboratories. We report about almost Fourier-limited pulses with a duration close to 100 fs obtained in the single-pulse regime. The SDL cavity consisted of only three elements, an InGaAs/AlGaAs gain chip, a fast semiconductor saturable absorber mirror and an output coupler. The pulse in our mode-locked SDL was shaped mainly by the spectro-temporal behavior of saturable absorption and gain and the associated self-phase modulation. The group delay dispersion is small. Pulses as short as 107 fs were generated with a spectral width of 10.2 nm (FWHM), centered at 1030 nm. This results in a time-bandwidth product of ≈0.31, which is close to the transform-limit. The output power amounted to 3 mW at a pulse repetition rate of 5 GHz, corresponding to fundamental mode-locking. Harmonically mode-locked SDLs are capable of operating at much higher pulse repetition rates, which was also investigated. A maximum pulse repetition rate of 92 GHz was achieved while preserving the pulse duration shorter than 200 fs.